This invention generally relates to golf balls with high coefficient of restitution and low deformation, and more particularly to a high coefficient of restitution golf ball at high club speeds.
Golf balls have been designed to provide particular playing characteristics. These characteristics generally include initial ball velocity, coefficient of restitution (CoR), compression, weight distribution and spin of the golf ball, which can be optimized for various types of players.
Golf balls can generally be divided into two classes: solid and wound. Solid golf balls include single-layer, dual-layer (i.e., solid core and a cover), and multi-layer (i.e., solid core of one or more layers and/or a cover of one or more layers) golf balls. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by tensioned elastomeric thread, and a cover.
Generally, the hardness of a golf ball or a golf ball core is one among other factors used in designing golf balls. Typically, when a ball is hard, e.g., possessing high compression values and low deformation when struck by a club, it typically has high CoR and high initial velocity after impact with a golf club. However, hard ball has a xe2x80x9chardxe2x80x9d feel and is difficult to control on the greens. A softer ball, e.g., lower compression value and high deformation, has a xe2x80x9csoftxe2x80x9d feel and is easier to control with short iron clubs for greenside play. Recently developed solid balls have a core, at least one intermediate layer, and a cover. The intermediate layer improves other playing characteristics of solid balls, and can be made from thermoset or thermoplastic materials.
Recent advancements in golf ball design can produce golf balls with low compression for soft xe2x80x9cfeelxe2x80x9d and high CoR for long flight distance. The CoR for low compression balls, however, decreases at higher impact speed with golf clubs.
Hence, there remains a need in the art for low compression golf balls that have high coefficient of restitution at low impact speeds and at high impact speeds.
Hence, the present invention is directed to a golf ball that has high coefficient of restitution at all impact speeds.
The present invention is also directed to a golf ball that has high coefficient of restitution at high and low impact speeds while maintaining soft feel and control characteristics.
The present invention strikes a balance between a soft core, which provides a soft feel to the player but suffers from low coefficient of restitution at high club head speeds, and a hard core, which provides a higher coefficient of restitution but suffers from a hard feel to the player.
The present invention is directed to a golf ball comprising an innermost core, a cover and an intermediate layer disposed between the innermost core and the cover, wherein one of either the core or the intermediate layer comprises a rubber composition containing a halogenated organosulfur compound, and wherein the other of either the core or the intermediate layer has a compression of greater than about 60 PGA, and wherein the golf ball has a coefficient of restitution of greater than about 0.81 at about 125 feet per second. The rubber composition preferably comprises at least about 2.2 parts per hundred of the halogenated organosulfur compound, and preferably the halogenated organosulfur compound is pentachlorothiophenol or a zinc salt of pentachlorothiophenol.
The compression is preferably greater than about 80 PGA, and more preferably greater than about 90 PGA. The coefficient of restitution of the ball is greater than 0.75 at 160 feet per second, and more preferably greater than 0.76 at 160 feet per second. In accordance to one aspect of the present invention, the intermediate layer is formed from the rubber composition. On the other hand, the core can be formed from the rubber composition.
In accordance to one embodiment, the present invention is directed to a golf ball comprising an innermost core, a cover and an intermediate layer disposed between the innermost core and the cover, wherein the intermediate layer comprises a rubber composition containing a halogenated organosulfur compound, and wherein the core and the intermediate layer have a compression of greater than about 60 PGA. Preferably, the compression is greater than about 80 PGA, and more preferably greater than about 90 PGA. This golf ball has coefficient of restitution of at least about 0.81 at about 125 feet per second, and coefficient of restitution of at least about 0.76 at about 160 feet per second.
The intermediate layer has a hardness of about 25 to about 70 on the Shore C scale. Preferably, the intermediate layer has a hardness of less than about 60 on the Shore C scale. On the other hand, the core has a hardness of at least about 70 on the Shore C scale, and the compression of the core is greater than about 70 PGA, and preferably greater than about 80 PGA.
The thickness of the intermediate layer is about 0.001 inch to about 0.100 inch, preferably about 0.010 inch to about 0.050 inch, and more preferably about 0.015 inch to about 0.035 inch. The diameter of the innermost core and the intermediate layer is at least about 1.500 inches.
In accordance to another embodiment, the present invention is directed to a golf ball comprising an innermost core, a cover and an intermediate layer disposed between the innermost core and the cover, wherein the core comprises a rubber composition containing a halogenated organosulfur compound, and wherein the core and the intermediate layer have a compression of greater than about 60 PGA. Preferably, the compression is greater than about 80 PGA, and more preferably greater than about 90 PGA. This golf ball has coefficient of restitution of at least 0.80 at 125 feet per second, and more preferably at least 0.81 at 125 feet per second.
The rubber composition of the core preferably comprises about 2.2 phr to about 5.0 phr of halogenated organosulfur compound, and the diameter of the core is less than about 1.500 inches. Preferably, the core has a compression of less than about 60 PGA and more preferably less than about 50 PGA. The thickness of the intermediate layer is at least about 0.090 inch, and preferably between about 0.090 inch and about 0.180 inch. The intermediate layer comprises a laminate, and may comprise a blend of a fatty acid salt highly neutralized polymer and a high stiffness partially neutralized ionomer. The intermediate layer has a flexural modulus of greater than about 50,000 psi, and preferably greater than about 60,000 psi. More preferably, the flexural modulus of the intermediate layer is between about 50,000 psi to about 150,000 psi.
In an example of this embodiment, the innermost core has a diameter of from about 0.800 to about 1.400 inches and a compression of less than about 30 PGA, and the intermediate layer has flexural modulus of at least about 50,000 to at least about 70,000 psi and a thickness of about 0.110 inch, and the cover comprises thermoset polymer having a hardness from about 45 to about 60 on the Shore D scale and a thickness from about 0.020 inch to about 0.040 inch.
In accordance to yet another embodiment, the present invention is directed to a golf ball comprising an innermost core and a cover, wherein an inner cover layer of the cover comprises a rubber composition containing a halogenated organosulfur compound, and wherein the core has a compression of greater than about 60 PGA, wherein the golf ball has a coefficient of restitution of at least 0.80 at 125 feet per second. The halogenated organosulfur compound is preferably pentachlorothiophenol, or a zinc salt of pentachlorothiophenol. The cover may further comprise an outer cover layer and an intermediate cover layer disposed between the outer cover layer and the inner cover layer. The cover preferably has a thickness of less than about 0.125 inch. The inner cover layer preferably has a thickness in the range of about 0.005 inch to about 0.100 inch, more preferably about 0.010 inch to about 0.090 inch and most preferably about 0.015 inch to about 0.070 inch. The core has a diameter in the range of at least 1.400 inches, and has compression greater than about 80 PGA and preferably greater than about 90 PGA.